The title complexes were prepared from no-carrier-added99mTc–TcO
and the air-sensitive reducing ligand DMPE under argon in ethanol-water. At acidic pH [Tc(III)Cl2 dmpe2]+ was formed, while alkaline pH led to the formation of [Tc(I)dmpe3]+. About 150°C and at least 10–3M DMPE was needed to achieve over 95% yield in less than 1 hour, otherwise the [Tc(V)O2dmpe2]+ intermediate was present. Electrophoresis demonstrated the unit positive charge and reversed-phase ion-pair HPLC provided separation and identification of99mTc-products by direct comparison with known99Tc-complexes. In rats the99mTc-complexes were excreted by kidneys and liver and reached high heart/blood but only low heart/lung and heart/liver ratios. In dogs satisfactory myocardial scintigrams were obtained in spite of high liver activity.